The differential batch microcalorimeter has been rebuilt and improved both mechanically and thermally to give a long term stability of plus or minus .02 micro watts. Application to the study of the heat evolution from a tissue culture preparation of mouse tumor cells indicate 90 micro watts are evolved during endogenous metabolism aerobically. The differential pH-thermal titration apparatus has been modified to handle a titrant volume of 400 microliters, a combination pH electrode with calomel reference, and an S-100 bus microprocessor for collecting and storing the data. Using the microprocessor as a terminal, the data is then transferred to the DEC-PDP-10 for data processing. Improvements in the system permit a thermal sensitivity of 40 microcalories and 1 milli pH unit to be made.